const fp = require('lodash/fp');
// 数据
// horsepower 马力， dollar_value 价格， in_stock 库存
const cars = [
    {
        name: 'Ferrari FF',
        horsepower: 660,
        dollar_value: 700000,
        in_stock: true
    },
    {
        name: 'Spyker  C12 Zagato',
        horsepower: 650,
        dollar_value: 648000,
        in_stock: false
    },
    {
        name: 'Jaguar XKR_S',
        horsepower: 550,
        dollar_value: 132000,
        in_stock: true
    },
    {
        name: 'Audi R8',
        horsepower: 525,
        dollar_value: 114200,
        in_stock: false
    },
    {
        name: 'Aston Martin One-77',
        horsepower: 750,
        dollar_value: 1850000,
        in_stock: true
    },
    {
        name: 'Pagani Huayra',
        horsepower: 700,
        dollar_value: 130000,
        in_stock: false
    }
];

const _average = function (xs) {
    return fp.reduce(fp.add, 0, xs) / xs.length
}

const averageDollarValue = fp.flowRight(_average, fp.map(fp.prop('dollar_value')));
console.log(averageDollarValue(cars));